I wish to find a circuit to use that should have a variable INPUT of 20-400 volts DC. The OUTPUT must be a steady 27.2 volts AC. I must also be able to vary or control the OUTPUT amperage.

Any help will be greatly appreciated.

 

OUTPUT must be a steady 27.2 volts AC. I must also be able to vary or control the OUTPUT amperage.

Please be advised that these requirements are inconsistent... For a given load: dependance
of one parameter implies independence of the other...

Best regards
HP

 

What is the load current range?
Does the AC output have to be isolated from the DC input?
Why do you need a 20:1 input range?

ak

 

With a simple H-bridge with PWM control (or hysteresis-control) like the one shown you can get AC output of varaible frequency and amplitude. You can easily extend it to three-phase AC. Replace the voltage source U.1 by a DC/DC-converter (simple boost?, insulation?, bi-directional power flow? --> more information needed). The AC-source U.2 could be an AC-grid (or a motor and/or generator if it would be three-phase).

The AC-side current iout can be defined by your current control independently from the AC voltage U.2. The resulting current is sinusoidal plus a ripple, you can set phase and amplitude, but the frequency is the same as the AC-voltage frequency. The AC side current will follow iRef which you define according to your requirements. In case your AC-load is not a voltage source but e.g a resistor or inductor or current-source, you cannot control the output current (as already mentioned above).

Please note that the simulation above is a quick & dirty demonstration, the control is not optimized at all!